Field of the Invention
The invention relates to a method for recovering ruthenium from a spent ruthenium-based catalyst carried on aluminum oxide.
Description of the Related Art
Ruthenium is an expensive rare metal and has excellent catalytic performance and widespread application in catalyst industry. Ruthenium is often used in synthesizing ammonia, preparing cyclohexene through selective hydrogenation of benzene, and manufacturing fuel cells. Recovering ruthenium from a spent catalyst is a possible solution for recycling of the ruthenium resources.
One known method of recovering ruthenium includes the steps of: calcining a ruthenium catalyst carried on activated carbon at 600-1000° C. for 2-20 hours to obtain a grey black mixture; mixing the grey black mixture with KOH and KNO3, heating them at 300-950° C. for 1-5 hours, and cooling them to obtain an alkali fusion product; dissolving the alkali fusion product in water at 50-90° C. to obtain a K2RuO4 solution; adding NaClO and concentrated H2SO4 to the K2RuO4 solution and heating the mixture solution at 50-90° C. for 2-4 hours to obtain RuO4 gas; and using a strong acid solution to absorb the RuO4 gas and then distilling to obtain a ruthenium salt. The method is complicated and has high energy consumption and low recovery rate of ruthenium.
In addition, another method of preparing ruthenium powder includes: adding ammonium chloride to a hydrochloric acid solution containing ruthenium (III) to produce (NH4)3RuCl6 precipitate, calcining the (NH4)3RuCl6 in a hydrogen atmosphere to produce ruthenium powder. This method is capable of producing high quality ruthenium powder. However, because (NH4)3RuCl6 is highly water-soluble, the ruthenium cannot be completely precipitated from the solution and, therefore, the recovery rate of ruthenium is very low.